In conventional group call services, including Voice Group Call Service (VGCS) and Voice Broadcast Service (VBS), each nominated cell in a given call uses an independent A-interface circuit. However, when a group call involves numerous cells, initiation of the group call consumes a large amount of A-interface circuit resources.
Conventionally, there are two schemes for sharing the A-interface in group call services. A first scheme is to share an A-interface circuit. In this scheme, a Mobile Switching Center (MSC) independently sends an Assignment Request message for each of nominated cells. A Call Instance Code (CIC) in each Assignment Request message is the same, since all cells share one A-interface circuit. A second scheme is to share an A-interface link, in addition to the A-interface circuit. When an MSC sends an Assignment Request message, a list of all cells involved in a given group call is contained in the Assignment Request message. If the number of nominated cells is so large that the entire list of all cells does not fit into the Assignment Request message, the MSC will send one or more subsequent VGCS/VBS AREA CELL INFO messages, containing remaining list of the cells.
One CIC is used in the Assignment Request message. The Assignment Request message contains information that indicates wireless channel assignment strategies for nominated cells. However, cells that belong to one Base Station Controller (BSC) must use the same assignment strategy, regardless of user distribution in each cell.
Therefore, there is a need for a wireless channel assignment system, which saves A-interface resources, and accommodates user needs in nominated cells of a given group call.